Equid herpesvirus 1 is neurotropic in mice, but latency from which infectious virus can be reactivated does not occur.

The research attempts to assess the potential of mice as models for the study of Equid herpesvirus 1 (EHV-1), a common virus causing abortion in horses. Notably, the study delves into latency and reactivation of EHV-1 in mice after infection but finds that the mouse model is limited in its representation of the virus’ latency.

EHV-1 and Its Latency

• EHV-1 is a prominent cause of virus-induced abortion in horses. Post initial infection, it usually becomes latent, mostly in the respiratory tract lymph nodes.
• The virus’s genome can also be detected within the peripheral nervous system after the latency.

Using Mice as a Model

• The researchers attempted to use mice as models for investigating EHV-1 latency and how the virus can be reactivated.
• To confirm virus replication, intracerebral and intranasal infections were caused intentionally in mice aged three and seventeen days. Virus isolation and indirect immunofluorescence (IIF) in the brain were the methods used to do this.
• The infected mice tissues were collected eight weeks after the infection for studies on reactivation.

Reactivation of EHV-1

• In both groups of mice, no infectious virus was found when attempting to cocultivate the collected tissues post-infection.
• In vivo virus reactivation attempts were conducted using corticosteroids. The presence of the viral antigen was traced at low levels in various organs through IIF and through the expression of the gB gene by reverse transcription polymerase chain reaction (RT-PCR).
• The virus was again detected by IIF after tissues were exposed to growth medium incorporating pokeweed mitogen (PWM).

Conclusions

• These findings underline the limitations of using mice as models for EHV-1 latency studies. The ‘ineffective reactivation’ of the virus further complicates the scenario.
• This indicates the necessity for finding new or more appropriate models for studying EHV-1 latency and reactivation.